Such vertical field effect-controllable semiconductor components have long been prior art. On the one hand, they are known as VMOS field-effect transistors if the drain zone adjoining the inner zone is of the same conduction type as the inner zone. On the other hand, such field effect-controllable semiconductor components are known as IGBTs if the drain zone is designed as anode zone and is of the opposite conduction type to the inner zone.
Furthermore, the invention also relates to field effect-controllable semiconductor components comprising a semiconductor body of the first conduction type,
Such lateral field effect-controllable semiconductor components have been known as lateral MOSFETs for a long time.
The semiconductor components mentioned in the introduction are thoroughly discussed in the book by Jens Peer Stengl; Jeno Tihanti: Leistungs-MOSFET-Praxis [Power MOSFET Practice], 2nd edition, Pflaumverlag, Munich, 1992.
All of the semiconductor components mentioned in the introduction have the inherent disadvantage that the forward resistance R.sub.on of the drain-source load path increases as the dielectric strength of the semiconductor component increases, since the thickness of the inner zone or of the drift zone has to increase. In the case of VMOS MOSFETs, the forward resistance R.sub.on per unit area is approximately 0.20 ohm/m.sup.2 at a voltage of 50 V and rises to a value of approximately 10 ohm/m.sup.2, for example, at a reverse voltage of 1000 V.
In order to eliminate this disadvantage, U.S. Pat. No. 5,216,275 presents a vertical MOSFET in which, instead of a homogeneous, for example epitaxially grown inner zone, layers of the first and of the second conduction type are present alternately. The fundamental structure is shown there in particular in FIGS. 4 and 5 and the associated parts of the description. In particular, the alternating p-type and n-type layers are in that case respectively connected to the base zones and to the drain zones. However, this leads to a severe limitation in the design of a semiconductor component since the edge regions such as the base and drain regions, can no longer be configured freely.
The object of the present invention, therefore, is to develop the field effect-controllable semiconductor components mentioned in the introduction in such a way that, despite a high reverse voltage, a low forward resistance is present and the disadvantages evinced in the prior art are eliminated.